A driven axle for automotive vehicles is known whereby a drive shaft aligned generally longitudinally relative to the vehicle drives a pinion which is in meshing engagement with a crown wheel in an axle housing. The crown wheel drives a right hand drive shaft connected to a right hand wheel and also drives a left hand drive shaft connected to a left hand wheel, thereby propelling the vehicle. Typically the crown wheel will drive the right and left hand drive shafts via a differential assembly.
In order to ensure longevity of the crown wheel and pinion gears, it is important to ensure that the pinion is positioned in the correct longitudinal position relative to the crown wheel, and it is also important to ensure that the crown wheel is positioned at the correct lateral position relative to the pinion. For these reasons, typically the pinion will be shimmed to ensure it is in its correct longitudinal position. Typically, screw thread adjustments can be made to move the crown wheel laterally to ensure that it is also in its correct lateral position. In view of the necessary accuracy required for positioning of the crown wheel and the pinion, these components are typically mounted on a carrier as a sub-assembly. The correct positioning of the crown wheel and pinion can therefore be achieved on the carrier remotely from the associated vehicle, for example on a workbench. Once the settings have been correctly carried out, the sub-assembly of the carrier, crown wheel and pinion can then be fitted to the vehicle. By providing a carrier sub-assembly including a crown wheel and pinion, the crown wheel and pinion can be correctly positioned relative to each other in a clean environment, and then the carrier can be fitted to the vehicle with the fitting taking place in a traditionally less clean environment, typically beneath the vehicle where road dirt and the like will have accumulated.
In most vehicles the carrier sub-assembly will include a differential assembly, and as such the carrier is known as a “differential carrier”.
Such carriers or differential carriers will include a generally circular flange. The carrier sub-assembly will be assembled into the axle through a generally circular hole in the axle. The crown wheel, pinion and differential (if fitted) will pass through the hole in the axle and the carrier flange will then effectively close off the hole. Typically a series of bolts will fix the carrier flange to the axle.
Oil is provided in the axle housing for lubricating and cooling the crown wheel, pinion, differential gears and associated bearings. However, the rotation of the crown wheel, pinion and differential housing in this oil leads to power losses due to oil churning, thereby increasing the overall fuel consumption of the vehicle.